Prefabricated building structure

ABSTRACT

A prefabricated building structure of particular utility as a sauna lodge or steam room comprises horizontal tongue-and-groove wall planks which are rectangularly cut away at their ends to form longitudinally extending tenons. When the planks are disposed one above another, the tenons interfit and flanges provided on external corner holding members are received in slots formed in the outer faces of the planks to hold the planks together in their assembled disposition as well as to provide adequate sealing of the corner.

United States Patent [191 Williams June 25, 1974 PREFABRICATED BUILDING STRUCTURE 22 Filed: Jan.22, 1973 21 Appl. No.: 325,249

[52] U.S. Cl 52/79, 52/233, 52/288, 52/483 [51] Int. Cl E04b 1/10, E04h l/l2 [58] Field of Search 52/79, 233, 595, 288, 497, 52/480, 483

[56] References Cited UNITED STATES PATENTS 1,213,188 1/1917 Hahn 52/497 X 2,163,381 6/1939 Marsan 52/483 2,373,789 4/1945 Smith 52/282 3,229,431 1/1966 Paul 52/79 X 3,235,118 2/1966 Kew1ey.. 52/288 X 3,407,555 10/1968 Pugh 52/288 3,470,666 10/1969 Mot et al. 52/480 X 3,511,005 5/1970 MacMaster 52/595 X 3,521,41 7 1970 Onjukka 52/233 X 3,543,463 12/1970 Cannon 52/288 X FOREIGN PATENTS OR APPLICATIONS 1,008,894 5/1957 Germany 52/480 140,957 10/ l 934 Austria 867,559 4/1971 Canada 166,114 11/1949 Austria 52/233 Primary Examiner-Henry C. Sutherland Assistant ExaminerLeslie A. Braun 5 7 ABSTRACT A prefabricated building structure of particular utility as a sauna lodge or steam room comprises horizontal tongue-and-groove wall planks which are rectangularly cut away at their ends to form longitudinally extending tenons. When the planks are disposed one above another, the tenons interfit and flanges provided on external corner holding members are received in slots formed in the outer faces of the planks to hold the planks together in their assembled disposition as well as to provide adequate sealing of the corner.

10 Claims, 9 Drawing Figures PREFABRICATED BUILDING STRUCTURE The present invention relates to prefabricated building structures of the type in which the walls of such a structure are formed of horizontal tongue-and-groove planks. More particularly, this invention relates to corner, roof and ceiling constructions of particularly advantageous design for use in such prefabricated building structures and by means of which constructions a building structure can be prefabricated in a factory and assembled on a site by a purchaser with a minimum of tools and skill. The constructions of this invention are of particular utility in the fabrication of so-called steam rooms and sauna lodges which can be erected either indoors or out-of-doors since they facilitate the erection of such structures in confined spaces.

BACKGROUND OF THE INVENTION Several types of partially prefabricated wooden structures incorporating horizontal tongue-and-groove planks are already known. Typically such known systems incorporate relatively complex, notched and interlocking corner constructions. With many of the known structures, the services of skilled tradesmen are often required for the erection since the interfitting of the prefabricated notched comers of the planks becomes progressively more difficult as the structure is erected, particularly if the foundations are not absolutely level, modification of the interlocking planks often being required in the upper parts of such structures. As a result, the known structures can not easily be erected by unskilled persons. A typical form for such a known structure is shown in United States Letters Patent No. 3,189,950.

Many of the known interlocking comer structures for such prefabricated building structures prevent the use of such a structure in a confined space such as in the basement of a home where the owner may wish to erect a steam room since the corners of such a structure frequently project outwardly from the structure. As a result of such outwardly projecting comers, it is often impossible to erect such a structure in the corner of a basement so that it is flush with the basement walls. Even when such erection is possible, the structure maY occupy an uneconomical amount of space. Accordingly, it is desirable, if not essential, that the comer construction of such a prefabricated structure be made in such a way that it can be fitted so as to be flush with the inner walls of a basement while still incorporating adequate sealing means to prevent the escape of steam or the like from within the structure. Consequently, for the purpose of allowing such a building structure to be erected in a confined space, such as a basement, it is frequently necessary that such a structure should be capable of being erected entirely from the inside; if it were necessary to work around the outside of the structure, it would then often be impossible to erect it in such a confined space. A further desirable feature is that the corner construction of such a building structure be rugged and self-supporting so as to ensure long life and stability in use.

It is already known to employ various forms of comer construction incorporating lengths of metal anglesection for the purpose of holding together the ends of the planks forming the walls of such a building structure. There may be mentioned, for example, the comer constructions shown in United States Letters Patent Nos. 2,373,789 and 3,521,417. The comer constructions shown in those earlier patents, however, present various disadvantages. It can be indicated by way of example that one of the known comer constructions for such a building structure requires bolts to be inserted through the comers at vertically spaced intervals for the purpose of holding the metal angle-sections firmly in position. Since such bolts must be inserted from the outside of the metal angle inwardly through the corner of the building, a construction utilizing such bolts cannot be employed in a confined space where access to the outside of the corner is not possible. In another known form of corner construction employing planks which have their ends cut at angles permitting them to be assembled in end-abutting relationships, the planks are held together by means of an adjustable pressure clamping means located at the upper end of the anglesection. This construction is, however, somewhat cumbersome and expensive for use in a prefabricated building and,unless the planks are machined to very precise tolerances at their ends, the actual erection of the building is extremely difiicult for individual home owners as a result of the frictional forces between the end grain of one plank and the end grain of another plank during the interfitting of the planks.

Furthermore, the structures heretofore proposed do not provide an adequately insulated ceiling construction and make no specific provision for the assembly of door frames, window frames or the like, in a manner facilitating the production of an entirely prefabricated unit ready for assembly on site.

BRIEF SUMMARY OF THE INVENTION The present invention aims generally to provide a prefabricated building structure constructed of horizontally arranged tongue-and-groove planks and which structure incorporates corner constructions in which the planks are notched or cut away at their corners so as to interfit one above the other and thereby to form a rugged and self-supporting comer. A simple anglesection holding member is provided along the outside of each corner effectively to seal that comer and to hold the planks in their interlocked disposition without the use of additional fastening means, either from the outside of the corner or from the upper ends of the holding members.

Additionally, the present invention provides, in its notched interlocking corner construction, a system of interlocking plank surfaces in which the exposed end grain of one plank will lie against a smooth side grain surface of an adjacent plank thereby reducing to a minimum the frictional resistance inherent in such a corner construction during its assembly while still ensuring that an effective seal will be achieved at each corner.

Another object of this invention in accordance with a particularly useful feature thereof is to provide for the construction of a simple yet highly effective insulated roof assembly which can be erected from the inside of a building structure thereby in turn to facilitate the erection of such a structure in a confined space.

The invention also provides for the incorporation of prefabricated door frames and window frames, if desired, in a structure in accordance with the invention in a simple yet highly effective manner.

The foregoing and other features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention, which description is given by way of example only, with reference to the accompanying drawings in which like reference legends refer to like parts throughout the various views and diagrams.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective illustration of a sauna room constructed in accordance with the invention and with parts thereof shown cut away to reveal constructional details;

FIG. 2 is a sectional illustration showing the construction of the roof of the room shown in FIG. 1, the roof having been omitted from FIG. I for the sake of clarity;

FIG. 3 is an enlarged perspective illustration of a corner detail of the room structure shown in FIG. 1, with a metal angle-section holding member removed for the sake of clarity;

FIG. 4 is a top view of the comer construction of the structure shown in FIG. 3 with the holding member shown in position;

FIG. 5 shows the room structure of the preceding figures at a stage during its erection;

FIG. 6 is an exploded perspective view illustrating an alternative system for supporting a roof on the room structure shown in FIG. 1;

FIG. 7 is an enlarged and fragmentary vertical sectional view when taken as indicated by the arrow 77 of FIG. 6 and showing the roof in position as well as details for the optional mounting of a thermostat on the structure of the preceding figures;

FIG. 8 is a fragmentary exploded view showing a detail of an alternative door frame for the structure of FIG. 1; and

FIG. 9 is an exploded and fragmentary perspective view showing details of an alternative arrangement for mounting a bench in the structure of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. I of the accompanying drawings, it will be seen that the building structure accord ing to the invention as indicated generally therein at B comprises a plurality of relatively thick and massive plank members 10, which typically may be two or three inches thick to provide adequate heat insulation. The planks 1.0 are arranged in horizontal edge abutting relationship as shown. The planks 10 comprise outer plank surfaces 11 and inner plank surfaces 12 and are provided along their transverse top edges with mutually parallel and spaced apart upstanding tongues 13 and, along their bottom transverse edges, with parallel and spaced apart mating grooves 14.

Planks 10, when arranged in edge to edge abutting relationship as shown form a good air-tight and watertight seal as a result of the interfitting relationship of the tongues 13 in the grooves 14 as well as providing a highly effective wall construction without the use of any additional frame members.

The construction of the comers of the structure B will be described in greater detail hereinafter but it can be noted at this juncture that metal angle-section holding members referenced generally at 15 and fitting substantially flush with the other surfaces 11 of the planks 10 are provided. With the use of such angle-section holding members 15, the structure B can be erected closely adjacent to side walls W of a house or basement. Within the structure B, there may be provided benches generally indicated at 16 and consisting of horizontal and spaced apart planks fastened across the width of the structure B by any suitable means. Such benches can be installed, if desired, so that they can be removed, or at least tilted upwardly, for cleaning and the like. Alternatively, such benches can be permanently installed as will be described in greater detail hereinafter with reference to FIG. 7.

The structure B will normally includes a floor which is shown in FIG. 1 as including wooden planking 17, preferably comprising spaced apart individual planks, to permit water drainage to a sub-floor indicated at 18 and which sub-floor may be of poured concrete or the like and which will normally incorporate some form of drain means (not shown) coupled to the drainage system of the house. When used as a sauna room, the structure B will frequently incorporate a heater shown in phantom outline and indicated generally at H, such heater being usefully and preferably constructed in accordance with the teaching of Canadian Letters Patent No. 764,585, details of the construction of the heater H being omitted herefrom for the sake of clarity.

To provide access to the interior of the structure B, a door frame assembly generally indicated at 19 is provided.

Although not shown in FIG. I, a thermally insulated roof assembly can be provided as shown in FIG. 2, in which figure, such a roof assembly is indicated generally at 20. The construction of the roof 20 will be described in greater detail hereinafter. It will or course be understood that the structure B shown in FIG. 1 is illustrated as being in the form of a sauna lodge or steam room. If, however, a larger outdoor structure is required, it may be desirable to provide a window (not shown) and such a window can be provided in substantially the same way as the door frame. In addition, if the structure is to be erected out of doors for use other than as a steam room, the roof assembly 20 may be of different construction; for example, such a roof can include rafters, roof decking and weather-proofing material.

Referring now to FIGS. 1 and 3 it will be noted that the planks 10 in any two adjacent sides of the structure are vertically offset from one another. For this purpose, a half-width plank generally indicated at 10a will be used as a starter on two opposite sides of the build ing, as shown in FIG. 1. Similarly, half-width planks 10b (FIG. 6) will be used on the other pair of walls to pro vide a level roof-supporting frame.

The comer construction of the building structure B will now be described in greater detail with particular reference to FIGS. 3 and 4, the angle-section holding member 15 being omitted from FIG. 3 for the sake of clarity but being shown in FIG. 4 for the sake of completeness. From FIG. 3, it will be seen that the corner construction shown therein requires that, each end of each of the planks 10 is cut away as indicated at 21 to provide a rectangular sectioned tenon generally indicated at 24 and having inner and outer side grain surfaces 25 and 25a and an exposed end grain surface 25b, the exposed end grain surface of the plank 10 being indicated by the legend 22 and the top surface of the tenon .24 by the legend 23. A continuous vertical groove 26 is cut in the outer surface 11 of each of the planks 10 and each such groove 26 is defined by opposed and longitudinally spaced apart, inner and outer transverse surfaces 27 and 28 respectively, the surface 28 being substantially coplanar with the end grain surface 22 of the plank l0 and the surface 27 being longitudinally offset with respect thereto. The slot or groove 26 is usefully fonned to a depth equal approximately to one quarter the thickness of the plank 10, but, in any event, that groove will not normally extend beyond the outermost of the two parallel tongues 13. The tenon 24 preferably has a length less than the thickness of the plank 10, such length generally being equal to approximately two thirds of that thickness. In this way, the corner of the structure B is formed so that the tenon 24 of one plank only partially overlaps the next adjacent tenon 24 so that in turn the apex of the corner of the holding member can be curved or radiussed as shown. This more readily enables the corner of the structure to be fitted snugly into the comer between the two walls W of a basement and thereby saves space.

Each tenon 24 usefully has a transverse width equal to the thickness of the plank l0 and will be of such a heightv as to pennit the required interfitting of the planks 10.

The half-width starter plank 10a is formed at each of its ends in substantially the same manner as are the full height planks 10 with the exception that only the upper portion of the starter plank 10a is cut away, the plank 10a, therefore, to all intents and purposes being the same as the plank 10 with the exception that it has been cut along its longitudinal median line.

As more clearly shown in FIG. 4, each of the anglesection holding members 15 is formed with two mutually perpendicular legs 15a and 15b carrying flanges 29 which are received in respective ones of the grooves 26. Each holding member 15 is also formed with inturned end sealing lips 30 adapted to make continuous contact with the outer surfaces 11 of the planks 10 forming the respective corner of the structure B. In this way, the holding members 15 hold the planks 10 in their overlapping and interlocking engagement and also seal the structure against the passage of moisture therethrough. The holding members 15 are usefully formed as metal extrusions but the use of other materials is not precluded.

Reference will now be made to the roof assembly structure 20 shown in FIG. 2. It will be seen from that figure that the roof assembly 20 comprises spaced apart and parallel rafters 31 which are supported at their ends on opposite walls of the structure B, for example, by being nailed to the topmost rows of the planks 10. Each of the rafters 31 is cut away as indicated at 32 and 33 to provide upper and lower shoulders 32a and 33a respectively. Thermal insulation panels 34 formed of cork or other suitable insulating material and of appropriate dimensions are supported on the upper shoulders 32a of adjacent ceiling rafters 31, the panels 34 being inserted upwardly and obliquely between the rafters 31, turned back into a horizontal position and lowered into the position shown in FIG. 2. No specific fastening of the panels 34 in the illustrated position has been found to be necessary, although, if desired, such panels can be secured in position, for example, by means of an adhesive or otherwise.

A lower heat barrier is provided by corrugated heat resistant panels 35 which are preferably formed of corrugated paperboard or the like. Each of the panels 35 is usefully formed with a reflective undersurface 36 formed, for example, of aluminum foil, metallic paint or other appropriate coating applied to the undersurface of the panel 35. Spaced below the lower panels 35, there is usefully provided a moisture barrier sheet 37 consisting simply of a sheet of thermoplastic material of a size equal at least to the cross sectional area of the structure B itself, and preferably formed in adjacent continuous strips and fastened to the rafters 31 by means of metal staples or the like (not shown). To complete the roof assembly 20, ceiling lining planks 38 of wood or the like are attached below the barrier sheet 37 to the rafters 31 by nails (not shown), such planks 38 preferably being of simple tongue-and-groove construction so as to inhibit the passage of moisture. The structure of the roof assembly 20 is preferably such that substantial air spaces as shown in FIG. 2 are provided between the moisture barrier sheet 37 and the lower insulation panels 35 as well as between the lower insulation panels 35 and the upper thermal insulation panels 34 so as further to minimize the loss of heat. It will also be noted that the roof assembly 20 is of such a construction that it can readily be erected, placed in position and completed from the interior of the building B without requiring access to the outside of that building, which would clearly be impossible if the building B were being erected within the basement of a home.

The manner in which the structure B is assembled will now be briefly summarized. For this purpose, the half planks 10a, the planks 10 and the comer holding members 15 are mounted as shown on the sub-floor 18 to form the four walls of the structure. Fitting of the planks 10 is simply a matter of placing them one above the other and hammering them into position as shown in FIG. 5, working in successive courses around the structure. As each plank 10 is placed in position, that plank will be positioned so that it is spaced above the next lower plank l0 and each of the planks 10 will be moved so that the flanges 29 of the respective one of the holding members 15 fit within the aforementioned grooves 26. The planks 10 will then be forced downwardly, for example, by means of a mallet, as shown in FIG. 5, care being taken to avoid damage to the upstanding tongues 13 on the top surface of the plank. The tenon 24 at each end of each plank 10 will gradually interlock with those of the next lower plank 10 at each comer, with the side grain surfaces 25 and 25a of the tenon 24 sliding smoothly and easily across the adjacent end grain surface 22 thereby to facilitate easy assembly.

When all of the planks 10 have been so positioned, half planks 10b are then inserted on two of the walls of the structure to level the top edges of those walls. It will be understood that the door frame assembly 19, the floor planks 17 and the benches 16 will be installed at any approprate stage during erection of the structure B. Finally, the roof assembly 20 is fitted. For this purpose, the rafters 31 are first secured in position. The upper panels 34 are then inserted from below by twisting sideways, raising them upwardly through the space between two adjacent rafters 31 and lowering them into position on the upper shoulders 32a. The lower panels 35 are then fastened in position, for example, by means of staples or the like. The barrier film 37 is next stapled to the rafters 31 and the ceiling planks 38 are finally nailed in position to complete structure.

Although the invention is in no way restricted to any particular construction of the door frame 19 shown in FIG. 1, it will be seen from that figure that the door frame 19 shown therein includes jambs 41 and 42 and a sill 43. Each of the jambs 41 and 42 is formed with a recess 44 for receiving butt ends of the planks used in the respective ones of the walls of the structure B. In this particular door frame construction, it is not necessary to secure the individual planks to the jambs 41 and 42.

Referring to FIG. 8, there is shown therein an alternative construction for a door frame for use in a building structure in accordance with this invention. The door frame shown fragmentarily in FIG. 8 includes jambs 46 and a lintel 47 which are secured together in a conventional manner, a tenon 48 at each end of the lintel 47 being received in a slot 49 formed in the top end of a respective one of the jambs 46.

Referring next to FIGS. 6 and 7, it will be noted that there is shown therein one alternative manner for securing a roof on a prefabricated building structure in accordance with this invention. For this purpose, the topmost ones of the planks It) and the half planks 10b are cut away to provide upwardly facing supporting shoulders 51 on which roof planks 52 are supported in side by side orientation.

A thermostat generally indicated at 53 in FIG. 7 is mounted at a convenient position on the inner surface of an appropriate one of the walls of the structure and a control cable conduit 54 extends from the thermostat 53 through an opening 55 provided for such purpose in the roof of the structure. A mutually operable control switch indicated schematically at 56 and provided for adjusting the setting of the thermostat 53 is usefully provided as shown so that it can be operated from outside the structure.

Referring finally to FIG. 9 of the accompanying drawings, there is shown therein one alternative way for mounting a bench in a prefabricated building structure in accordance with this invention. The bench generally indicated at 70 in FIG. 9 includes a front cross member 71 and transverse joists 72. The cross member 71 is supported at each of its ends in openings 73 cut for this purpose in appropriate ones of the planks 10 while the rearward ends (not shown) of the joists 72 are usefully supported in the rear wall of the structure in the same manner. At their forward ends the joists 72 are secured to the cross member 71 by nails 74. It will be understood that the cross member 71 and the joists 72 are easily placed in their correct positions during the on-site erection of the structure. Seating planks 75 are supported on the top surfaces of the cross member 71 and of the joists 72 and, if desired, such seating planks can be permanently or releasably secured in position.

The foregoing is a description of a preferred embodiment of the invention which is given here merely by way of example, comprehending all such variations as come within the scope of the appended claims.

What I claim is:

l. A prefabricated building structure of the type comprising horizontal tongue-and-groove planks of a sufficient thickness for assembly into an insulated building in a confined space and which building structure comprises:

a pluraltiy of tongue-and-groove wooden planks having generally planar, generally mutually parallel and longitudinally extending inner and outer surfaces, each such plank being of a predetermined height and thickness, such planks being disposed in mutual tongue-and-groove edgewise horizontal mating engagement with each other to form the walls of said building structure and some of said planks having butt ends at one end thereof for defining a door opening;

a tenon defined by longitudinally extending faces and projecting longitudinally from a respective end of each said plank at each said corner of said structure and defined by upper and lower rectangularly cut away portions of said plank thereby locating the tenon intermediate the upper and lower edges of the plank each said tenon having a width essentially equal to the thickness of each said plank, a height equal to about one half the height of the plank such that the tenon interfits snugly with the tenons of adjacent said planks, and a longitudinal length which is less than said plank thickness whereby when a said plank is assembled at a corner with other planks the lower cut away portion thereof receives part of the tenon of the sub-jacent plank, and the upper cut away portion receives part of the tenon of the super-adjacent plank;

vertically extending grooves formed in outer surfaces of said planks for alignment of such grooves with each other when said planks are disposed in mating engagement as aforesaid thereby to form continuous vertical grooves in both walls adjacent each said comer of said building structure;

vertically extending holding members having generally L-shaped horizontal sectional configurations, each including two mutually perpendicular legs and adapted to fit snugly around a respective corner of said building structure;

flanges on said legs of each said holding member to fit within respective ones of said continuous vertical grooves and to interlock said planks in their assembled disposition;

sealing members on said legs of said holding members outwardly of said flanges for sealing engagement with said outer surfaces of respective ones of said walls;

a roof assembly mounted on said walls to enclose the upper part of said building structure;

door frame members adapted to be attached to said butt ends of said planks within said door opening; and

floor means within said building structure.

2. A prefabricated building structure as claimed in claim 1 in which each said vertically extending groove in each said plank is defined by opposed and longitudinally spaced apart outer and inner transverse surfaces, said outer transverse surface being essentially coplanar with a longitudinally inner transverse plane of a respective one of said tenons.

3. A prefabricated building structure as claimed in claim 1 in which each said holding member includes, in horizontal section, a curved corner portion from which said mutually perpendicular legs extend.

4. A prefabricated building structure as claimed in claim 3 in which said sealing members are formed as terminal lips on respective ones of said legs of said holding members.

5. A prefabricated building structure as claimed in claim 1 and which structure additionally includes upclaim 7 and which additionally comprises a ceiling extending between said walls and secured to undersurfaces of said rafters.

9. A prefabricated building structure as claimed in claim 1 in which each said holding member is formed of metal.

10. A prefabricated building structure as claimed in claim 1 in which each said holding member is an extru- Slon. 

1. A prefabricated building structure of the type comprising horizontal tongue-and-groove planks of a sufficient thickness for assembly into an insulated building in a confined space and which building structure comprises: a pluraltiy of tongue-and-groove wooden planks having generally planar, generally mutually parallel and longitudinally extending inner and outer surfaces, each such plank being of a predetermined height and thickness, such planks being disposed in mutual tongue-and-groove edgewise horizontal mating engagement with each other to form the walls of said building structure and some of said planks having butt ends at one end thereof for defining a door opening; a tenon defined by longitudinally extending faces and projecting longitudinally from a respective end of each said plank at each said corner of said structure and defined by upper and lower rectangularly cut away portions of said plank thereby locating the tenon intermediate the upper and lower edges of the plank each said tenon having a width essentially equal to the thickness of each said plank, a height equal to about one half the height of the plank such that the tenon interfits snugly with the tenons of adjacent said planks, and a longitudinal length which is less than said plank thickness whereby when a said plank is assembled at a corner with other planks the lower cut away portion thereof receives part of the tenon of the subjacent plank, and the upper cut away portion receives part of the tenon of the super-adjacent plank; vertically extending grooves formed in outer surfaces of said planks for alignment of such grooves with each other when said planks are disposed in mating engagement as aforesaid thereby to form continuous vertical grooves in both walls adjacent each said corner of said building structure; vertically extending holding members having generally L-shaped horizontal sectional configurations, each including two mutually perpendicular legs and adapted to fit snugly around a respective corner of said building structure; flanges on said legs of each said holding member to fit within respective ones of said continuous vertical grooves and to interlock said planks in their assembled disposition; sealing members on said legs of said holding members outwardly of said flanges for sealing engagement with said outer surfaces of respective ones of said walls; a roof assembly mounted on said walls to enclose the upper part of said building structure; door frame members adapted to be attached to said butt ends of said planks within said door opening; and floor means within said building structure.
 2. A prefabricated building structure as claimed in claim 1 in which each said vertically extending groove in each said plank is defined by opposed and longitudinally spaced apart outer and inner transverse surfaces, said outer transverse surface being essentially coplanar with a longitudinally inner transverse plane of a respective one of said tenons.
 3. A prefabricated building structure as claimed in claim 1 in which each said holding member includes, in horizontal section, a curved corner portion from which said mutually perpendicular legs extend.
 4. A prefabricated building structure as claimed in claim 3 in which said sealing members are formed as terminal lips on respective ones of said legs of said holding members.
 5. A prefabricated building structure as claimed in claim 1 and which structure additionally includes upwardly facing supporting surfaces for supporting said roof assembly.
 6. A prefabricated building structure as claimed in claim 5 in which said upwardly facing supporting surfaces for supporting said roof assembly are formed in uppermost ones of said planks.
 7. A prefabricated building structure as claimed in claim 5 in which said upwardly facing supporting surfaces are formed in rafters extending between opposed ones of said walls and secured to such walls.
 8. A prefabricated building structure as claimed in claim 7 and which additionally comprises a ceiling extending between said walls and secured to undersurfaces of said rafters.
 9. A prefabricated building structure as claimed in claim 1 in which each said holding member is formed of metal.
 10. A prefabricated building structure as claimed in claim 1 in which each said holding member is an extrusion. 